In a stacked projectile launcher the projectiles are fired sequentially from a stack contained in the barrel. These launchers offer an advantage in that the projectiles have no cartridges and can be fired electronically and relatively rapidly. However, propellant gases created by firing of the leading projectile can ignite the propellant charges that are provided for projectiles further down the stack. A sealing system is therefore required, such as forward or reverse wedging, in which a part of each projectile is forced into a circumferential contact with the bore the barrel. Alternatively the propellant charges may be sealed within chambers provided either externally to the barrel or internally to the projectiles themselves.
Another problem that must be overcome in stacked projectile launchers relates to the ease of loading and reloading. In some existing launchers the projectiles cannot be carried and loaded by operators in the field, so an empty launcher must be returned to base. In other launchers the projectiles must be carried and loaded as preformed stacks, so operators are faced with the dilemma of how to deal with a stack which has only been partially fired, in order to be fully prepared for the next event in e.g. a combat operation. An operator is unlikely to be comfortable carrying a partially loaded launcher into a life threatening situation, or carrying a partly empty stack back to base to be refilled.